Need Advice.. I'm Having Trouble Staying Under The 1000 Cal PreOp Diet

I am having trouble with staying under the 1000 calorie liquid diet preop diet. I have a slimfast with a banana blended into it in the morning, lunch and dinner, but with that all said and done, each of those are 305 calories each. So if I need to do anything else for a in between snack I am going over, I have been doing saltines and toast a few times a day as I just had leg surgery and the medicine makes me naseated. Does someone have some advice on something else I can drink other then slim fast to get my protien without the same calorie count? I have been trying to look up the information, but I get lost and confused when I look it up. My surgery date is June 17th, I am not sure why I am on a liquid diet this soon when I only have 4lbs more to loose, but the dr. put me on one. I feel so bad fofr going over, but really have no choice. Does anyone have some advice? I track everything I eat on the www.realizeband.com website as I am getting the realize band and when my dr sees it I doubt if it will go over well. I need advice.